Men who smoke increase their risk of having a stroke with every cigarette they have, researchers say.

They found smoking more than a packet of cigarettes a day doubles the risk of a stroke, compared to non-smokers.

The US study looked at the risk of hemorrhagic stroke, where ruptured blood vessels bleed in the brain. A third of them prove fatal within 30 days.

Smoking is already identified as a risk factor for the more common ischemic stroke, where the blood supply to the brain is blocked.

It has also linked with subarachnoid haemorrhage, a stroke where there is bleeding in the space between the brain and the skull.

Artery wall damage

Researchers from the Brigham and Women's Hospital, Harvard Medical School in Boston followed 22,000 male physicians from 1982 for an average of 18 years.

We urge smokers to reduce their risk of suffering a stroke by giving up

Stroke Association spokesperson

Information on smoking habits was collected at the beginning of the study after 24 months, 60 months and 144 months.

At the start of the research, half had never smoked, 40% were past smokers, 4% smoked less than a pack a day, and 7% smoked more.

Over the period of the study, over 1,000 men had strokes, including 139 hemorrhagic strokes.

Those who currently smoked had a 1.7 times higher risk of having all types of haemorrhagic stroke if they smoked less than 20 cigarettes a day and 2.4 times higher risk if they smoked more, when compared to men who never smoked.

Smokers also had double the risk of having a specific kind of hemorrhagic stroke called intracerebral haemorrhage, bleeding inside the brain.

The researchers say smoking may damage arterial walls, making arteries more prone to rupture.

Severe disability

Dr Tobias Kurth, who led the research, said: "Our results add to the multiple health benefits that can be accrued by abstaining from cigarette smoking."

A spokesperson for The Stroke Association said: "We urge smokers to reduce their risk of suffering a stroke by giving up.

"Stroke is the largest single cause of severe adult disability in the UK, with over 300,000 people affected at any one time."

The research is published in Stroke: Journal of the American Medical Association.